JP4947663B2 - Delay time determination method, peer node, and program in overlay network - Google Patents

Description

  The present invention relates to a delay time determination method, a peer node, and a program in an overlay network.

  FIG. 1 is a system configuration diagram of an overlay network.

  According to the system of FIG. 1, a plurality of peer nodes 1, a transmission source terminal 2 and a destination terminal 3 are connected to a physical network 4. On the physical network 4, an overlay network 5 is virtually configured by a plurality of peer nodes 1. A typical example of the overlay network is a P2P (Peer to Peer) network. The P2P network covers (overlays) the IP layer and enables interconnection between terminals. According to FIG. 1, the source terminal 2 and the destination terminal 3 function as SIP-UA (SIP-User Agent) for the peer node 1, and an overlay network is constructed by, for example, P2PSIP (Peer to Peer-Session Initiation Protocol). ing.

  In recent years, as a representative example of structured overlay, there is a technique of “Distributed Hash Table (DHT)” that distributes and manages data between terminals based on a hash value of a keyword. Unlike the conventional P2P technology represented by Napster or Gunutella, the “distributed hash table” can search data distributed in the entire network at high speed. In addition, the network can be reconstructed in an autonomous and distributed manner with respect to frequent participation and withdrawal of peer nodes.

  A typical example of the distributed hash table is “Chord” (see Non-Patent Document 1, for example). Chord considers a ring-shaped (annular) hash space in which the identification value increases clockwise. The identification value is a value of the SHA1 hash function. One of the features of the distributed hash table is scalability. The maximum number of peer nodes relayed when searching for address information is log (N), and the average value is guaranteed to be 0.5 × log (N) (N is the total number of peer nodes). Therefore, an efficient search is possible even when the number of peer nodes increases.

  FIG. 2 is an explanatory diagram of a structured overlay using Chord.

  According to FIG. 2, each peer node constituting the overlay network is mapped to a ring-shaped hash space. As the identification value to which the peer node is mapped, for example, a value obtained from the hash function with the IP address and port number of the peer node as input is determined as the node identification value.

  For example, it is assumed that the transmission source terminal (alice@auone.jp) is connected to the peer node ID 8 in the ring-shaped hash space. At this time, in order to search the registration information of the destination terminal (bob@auone.jp), it is assumed that the transmission source terminal inputs the address (bob@auone.jp) of the destination terminal to the hash function and obtains ID39. Then, the transmission source terminal searches for the ID 39 in which the registration information of the destination terminal is registered.

  Here, “successor list” and “finger table” are used. The “successor list” holds information of a plurality of peer nodes adjacent in the hash space. Therefore, when the identification value k of the peer node is given, the first existing peer node can be obtained by tracing clockwise.

  In the “finger table”, as a routing table, a number x obtained by adding 2 k powers (1, 2, 4, 8, 16...) To the identification value (for example, ID8) of the peer node and the number x And the identification value of the peer node of the successor (x).

  FIG. 2 is an example of a 6-bit hash identification value space, and the number of rows in the finger table is six (for example, in the case of a 160-bit hash identification value space, the number of rows in the finger table is 160). Here, assuming that peer nodes are assigned to all identification values, a case where hash (bob@auone.jp) = ID39 is looked up will be described.

(Hop 1) According to the finger table of ID8, the number closest to ID39 is 24 of 8 + 2 ⁴ (16). ID8 forwards the lookup message to ID24.
(Hop 2) According to the finger table of ID 24, the number closest to ID 39 is 24 + 2 ³ (8) = 32. ID 24 then forwards the lookup message to ID 32.
(Hop 3) According to the finger table of ID32, ID39 is also close to 32 + 2 ² (4) = 36. ID 32 then forwards the lookup message to ID 36.
(Hop 4) According to the finger table of ID36, ID39 is also close to 36 + 2 ¹ (2) = 38. ID 36 then forwards the lookup message to ID 38.
(Hop 5) According to the finger table of ID38, ID39 is also close to 38 + 2 ⁰ (1) = 39. ID 36 then forwards the lookup message to ID 39.
Accordingly, the peer node ID 8 can transfer the lookup message to the ID 39 and obtain registration information of bob@auone.jp.

  According to IETF (Internet Engineering Task Force), “P2PSIP” technology is disclosed in which autonomous distributed network architecture technology called P2P (Peer-to-Peer) is integrated with SIP signaling control (for example, non-P2PSIP). (See Patent Document 3). According to P2PSIP, a sessionless function by SIP (CSCF function in IMS / MMD) is installed in a peer node, thereby realizing a serverless system. By using P2P, distributed management and distributed control of information among peer nodes is executed, so that it is not necessary to increase the server system even when the number of subscribers increases.

  There is a technique that defines messaging required when an overlay network is constructed or data is searched (for example, see Non-Patent Document 2). Specifically, RELOAD (REsource LOcation And Discovery) is specified.

  There is also a technique for executing diagnosis within an overlay network (see, for example, Non-Patent Document 3). According to this technique, a transmission source terminal that performs diagnosis transmits an Echo request message toward a destination identification value, thereby measuring the number of relay terminals and a delay time to the destination terminal that manages the identification value. In addition, information on the operating time (Uptime) of the program at the destination terminal and free disk capacity can also be acquired. Further, in addition to the Ping mode in which only the destination terminal transmits the Echo response message, a Traceroute mode in which all peer nodes that relay the Echo request message transmit the Echo response message to the transmission source terminal is also defined. By using this mode, it is possible to detect a loop in the network, identify a bottleneck, and detect a malicious terminal.

Ion Stoica, Robert Morris, David Karger, M. Frans Kaashoek, and Hari Balakrishnan, “Chord: A Scalable Peer-to-peer LookupService for Internet Applications”, Proc. ACM SIGCOMM'01, San Diego, Sept. 2001. IETF Internet Draft: “REsource LOcation AndDiscovery (RELOAD)”, draft-ietf-p2psip-reload-00.txt IETF Internet Draft: “Diagnose P2PSIPOverlay Network Failures”, draft-zheng-p2psip-diagnose-02

  However, according to the P2PSIP network, when the number of peer nodes becomes enormous, the number of relay nodes when searching for address information of the destination terminal also becomes enormous. In particular, session control that requires real-time performance has a problem that the session establishment time increases. For example, assuming that the number of peer nodes is 10 million and the delay time between peer nodes is 50 milliseconds, the session establishment time is estimated to be 4.6 seconds at the maximum. The telecommunications equipment rules for business established by the Ministry of Internal Affairs and Communications stipulate that “the probability that the session setup time (Connection Setup-Delay) will be 3 seconds or more shall be 0.01 or less”. Can not provide.

  According to the techniques described in Non-Patent Documents 1 and 2, no technique is disclosed for determining the delay time during data search.

  According to the technique described in Non-Patent Document 3, it is possible to measure one-way / round-trip delay between a transmission source terminal and a destination terminal by adding time stamp information to an Echo message. However, this measurement requires an Echo message to be transmitted over the overlay network, and the delay time cannot be determined immediately when a destination identification value is given.

  Accordingly, the present invention provides a delay time determination method, a peer node, and a program that can immediately determine whether or not the delay time for the peer node is within a specified time based on the destination identification value in the overlay network. With the goal.

According to the present invention, there is provided a delay time determination method in an overlay network virtually configured on a physical network connected by a plurality of peer nodes,
Each peer node has a routing table in which the next peer node having an identification value communicable in one hop is registered, and an excess delay list in which an identification value range in which the delay time is equal to or longer than a specified time is registered,
A first step in which each peer node measures a delay time with a next peer node registered in the routing table;
A second step in which the source peer node transmits a request message including the destination identification value to the next peer node registered in the routing table;
A third step in which the relay peer node further forwards the received request message to the next peer node;
A fourth step in which when a relay peer node receives a response message corresponding to the request message, it adds a delay time to the next peer node that transmitted the response message and forwards the response message;
When the transmission source peer node receives the response message, the transmission source peer node sequentially adds the delay time between the hopped relay peer nodes from the transmission source peer node, and the identification value range after the next peer node where the delay time is equal to or longer than the specified time. A fifth step of registering to the excess delay list;
When the transmission source peer node further transmits the request message, it has a sixth step of determining whether or not the destination identification value of the request message is included in the excess delay list.

  According to another embodiment of the delay time determination method of the present invention, the source peer node may be a relay peer node that forwards the request message received from the first peer node to the second peer node.

  According to another embodiment of the delay time determination method of the present invention, the RTT (Round Trip Time) value is measured by periodically transmitting a Keep-Alive message to the next peer node registered in the routing table, It is also preferable to calculate the delay time from the RTT value.

According to another embodiment of the delay time determination method of the present invention,
A source peer node sending a delayed search request message including a destination identification value to a next peer node registered in the routing table;
When the relay peer node receives the delayed search request message, and the destination identification value of the search request message is included in the excess delay list of the relay peer node, the relay peer node returns a delay excess notification message. Is also preferable.

According to another embodiment of the delay time determination method of the present invention,
The peer node sends a list request message including an identification value space to a next peer node;
It is also preferable that the next peer node returns a list information that overlaps with the identification value space in the excess delay list held by the next peer node.

  According to another embodiment of the delay time determination method of the present invention, when the next peer node receives a list request message, the list information having a wide identification value range in the delay excess list is preferentially returned. Is also preferable.

According to another embodiment of the delay time determination method of the present invention,
The delay excess list further includes a registration time for each entry of the identification value range,
When the next peer node receives a list request message including the previous time, it is preferable that the list information of the identification value range in which the registration time after the previous time is recorded in the excess delay list is returned.

According to another embodiment of the delay time determination method of the present invention,
The overlay network protocol is a structured overlay Chord using a distributed hash table (DHT).
The routing table is also preferably a finger table.

According to the present invention, a peer node in an overlay network virtually configured on a physical network connected by a plurality of peer nodes,
A routing table in which a next peer node having an identification value communicable in one hop is registered;
Excess delay list with registered identification value range where the delay time is more than the specified time,
A delay time measuring means for measuring the delay time for each next peer node registered in the routing table;
A source request means for transmitting a request message including a destination identification value to the next peer node registered in the routing table;
A relay side request transfer means for further transferring the received request message to the next peer node;
When a response message corresponding to the request message is received, a relay side response transfer means for adding and transferring a delay time with the next peer node that has transmitted the response message;
When the response message is received, the delay time between the hopped relay peer nodes is added in order from the source peer node, and the identification value range after the next peer node whose delay time is equal to or longer than the specified time is added to the delay excess list. A source list registration means for registering with
And a transmission source delay time determination unit that determines whether the destination identification value of the request message is included in the excessive delay list when the request message is further transmitted.

  According to another embodiment of the peer node of the present invention, the delay time measuring means measures the RTT value by periodically transmitting a Keep-Alive message to the next peer node registered in the routing table, and the RTT value is measured. It is also preferable to calculate the delay time from

According to another embodiment in the peer node of the present invention,
A source search means for transmitting a delayed search request message including a destination identification value to the next peer node registered in the routing table;
When a delayed search request message is received, when the destination identification value of the search request message is included in the delay excess list of the relay peer node, relay side delay excess notification means is provided for returning a delay excess notification message. It is also preferable.

According to another embodiment in the peer node of the present invention,
An excess delay list request means for transmitting a list request message including an identification value space to a next peer node;
It is also preferable to have an excess delay list replying means for returning list information that overlaps with the identification value space in the excess delay list held by the next peer node.

  According to another embodiment of the peer node of the present invention, it is also preferable that the excess delay list reply means preferentially returns list information having a wide identification value range in the excess delay list.

According to the present invention, there is provided a program for causing a computer mounted on a peer node in an overlay network virtually configured on a physical network connected by a plurality of peer nodes to function.
A routing table in which a next peer node having an identification value communicable in one hop is registered;
Excess delay list with registered identification value range where the delay time is more than the specified time,
A delay time measuring means for measuring a delay time between the next peer node registered in the routing table;
A source request means for transmitting a request message including a destination identification value to the next peer node registered in the routing table;
A relay side request transfer means for further transferring the received request message to the next peer node;
When a response message corresponding to the request message is received, a relay side response transfer means for adding and transferring a delay time with the next peer node that has transmitted the response message;
When the response message is received, the delay time between the hopped relay peer nodes is added in order from the source peer node, and the identification value range after the next peer node whose delay time is equal to or longer than the specified time is added to the delay excess list. A source list registration means for registering with
When the request message is further transmitted, the computer is caused to function as a transmission source delay time determination unit that determines whether or not the destination identification value of the request message is included in the excessive delay list.

  According to the delay time determination method, peer node, and program of the present invention, it is possible to immediately determine whether or not the delay time for the peer node is within a specified time based on the destination identification value in the overlay network.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  Each peer node in the present invention has a “routing table” and an “excess delay list”. The “routing table” registers the next peer node having an identification value communicable in one hop from the identification value of the peer node. In the case of Chord, it means a finger table.

  The “delay excess list” registers an identification value range in which the delay time is equal to or longer than the specified time. Before transmitting the request message for the destination identification value, the peer node determines whether the destination identification value falls within the identification value range registered in the excess delay list. If applicable, the peer node can recognize that the delay time for the destination identification value requires a specified time or more.

  FIG. 3 is a sequence diagram in the present invention.

  FIG. 4 is an explanatory diagram showing the step of S31 in FIG.

  FIG. 5 is an explanatory diagram showing steps S32 to S36 in FIG.

(S31) Each peer node periodically transmits a Keep-Alive message and receives a response message for each next peer node registered in the routing table. According to Chord, the identification value of the peer node of the successor having the value obtained by adding 2 ^m (m = 159, 158,..., 0) added to its own peer node ID is registered as the next peer node in the finger table. Thereby, each peer node measures the delay time RTT with the next peer node. The delay time is stored in the routing table.

According to FIG. 3, peer node ID 8 transmits a Keep-Alive message to ID 24 registered in the finger table and receives a response. As a result, the peer node ID8 measures the delay time D (8-24) with the ID24.
D (xy): delay time between IDx and IDy

  Similarly, according to FIG. 3, the peer node ID 24 measures the delay time D (24-32) with the ID 32 registered in the finger table. The peer node ID 32 measures a delay time D (32-36) with the ID 36 registered in the finger table. Further, the peer node ID 32 measures a delay time D (32-36) between the peer node ID 32 and the ID 36 registered in the finger table. Further, the peer node ID 36 measures the delay time D (36-38) between the peer node ID 36 and the ID 38 registered in the finger table. Further, the peer node ID 38 measures the delay time D (38-39) between the peer node ID 38 and the ID 39 registered in the finger table.

(S32) The source peer node ID 8 transmits a request message including the destination identification value to the next peer node ID 24 registered in the routing table. Note that the relay peer node that relays the request message may operate as a source peer node in the present invention.

(S33) The relay peer node ID 24 further forwards the received request message to the next peer node ID 32. Further, the relay peer node ID 32 further transfers the received request message to the next peer node ID 36. Further, the relay peer node ID 36 further transfers the received request message to the next peer node ID 38. Further, the relay peer node ID 38 further transfers the received request message to the destination peer node ID 39.

(S34) The destination peer node ID 39 returns a response message to the relay peer node ID 38 in response to the received request message.

  The relay peer node ID 38 transfers the received response message to the relay peer node ID 36. At this time, the relay peer node ID 38 adds the relay identification value ID 38 and the delay time D (38-39) between the peer node IDs 39 to the response message. Further, the relay peer node ID 36 transfers the received response message to the relay peer node ID 32. At this time, the relay peer node ID 36 adds the relay identification value ID 36 and the delay time D (36-38) between the peer node IDs 38 to the response message. Further, the relay peer node ID 32 transfers the received response message to the relay peer node ID 24. At this time, the relay peer node ID 32 adds the relay identification value ID 32 and the delay time D (32-36) between the peer node ID 36 to the response message. Further, the relay peer node ID 24 transfers the received response message to the relay peer node ID 8. At this time, the relay peer node ID 24 adds the relay identification value ID 24 and the delay time D (24-32) between the peer node IDs 32 to the response message.

(S35) When the transmission source peer node receives the response message, the transmission source peer node sequentially adds the delay time between the hopped relay peer nodes from the transmission source peer node. Then, the identification value range after the next peer node whose delay time is equal to or longer than the specified time is registered in the excess delay list.

  In the excess delay list, the start (From) and end (To) representing the identification value space, and the registration time are recorded. For example, according to FIG. 3, the peer node ID 8 is in the order from the own node (D (8-24) → D (24-32) → D (32-36) → D (36-38) → D (38− 39)) is added with a delay time. Here, it is assumed that at the time of D (8-24) + D (24-32), the specified time is exceeded. If so, the identification value spaces of ID32 (From) to ID39 (To) are registered in the excessive delay list, assuming that they are excessively delayed.

(S36) When the transmission source peer node further transmits a request message (for example, at the time of data retrieval), it is determined whether or not the destination identification value of the request message is included in the excessive delay list. If the destination identification value is included in the excess delay list, it is determined that the delay time of the request message requires more than a specified time, otherwise, the delay time is determined to be shorter than the specified time. . Then, the source peer node transmits a request message to the next piano.

  FIG. 6 is an explanatory diagram showing the transfer of the delayed search request message.

  According to FIG. 6, the source peer node ID 8 transmits a delayed search request message including the destination identification value to the next peer node ID 24 registered in the routing table. At this time, the delayed search request message includes ID 39 as a destination identification value. When receiving the delayed search request message, the peer node ID 24 serving as the relay peer node determines whether or not the destination identification value ID 39 of the search request message is included in the delay excess list of the relay peer node. According to FIG. 6, since ID39 is included in the excess delay list of ID24, the relay peer node ID24 returns a delay excess notification message to ID8. Accordingly, the peer node ID 8 can be recognized as exceeding the specified time for the destination identification value ID 39. If ID39 is not included in the excess delay list of ID24, the relay peer node ID24 transfers the delay search request message to the next node.

  FIG. 7 is an explanatory diagram showing transfer of the list request message.

  According to FIG. 7, the peer node ID 8 transmits a list request message including an identification value space (ID 24 to ID 39) to which the message is to be transferred, to the next peer node ID 24. The next peer node ID 24 returns list information that overlaps with the identification value space (ID 24 to ID 39) in the retained delay excess list. According to FIG. 7, since the peer node ID 24 has registered ID 36 to ID 39 in the excessive delay list, this entry is returned to the peer node ID 8.

  In addition, when the next peer node receives the list request message, it is preferable that the list information having a wide identification value range in the excessive delay list is preferentially returned. If excess delay is detected for a wide range of identification values, that information should be shared by as many peer nodes as possible.

  Furthermore, it is preferable that the delay excess list further includes a registration time for each entry of the identification value range. In this case, the transmission source peer node includes the previous time in the list request message. The next peer node that has received this list request message returns the list information of the identification value range in which the registration time after the previous time is recorded in the excess delay list. As a result, transfer of duplicate list information can be avoided.

  In addition, the delay excess list further includes a registration time for each entry in the identification value range, so that an entry after a predetermined time can be deleted. In this case, the transmission source peer node needs to periodically transmit a request message and update the registration time.

  FIG. 8 is a functional configuration diagram of the peer node in the present invention.

  The peer node 1 is connected to an overlay network virtually configured on a physical network. According to FIG. 8, the peer node 1 includes the routing table 101, the excess delay list 102, the delay time measurement unit 103, the transmission source request unit 111, the transmission source list registration unit 112, and the transmission source delay time determination unit 113. A source search unit 114, a relay side request transfer unit 121, a relay side response transfer unit 122, a relay side delay excess notification unit 123, a delay excess list request unit 131, and a delay excess list reply unit 132. Have. These functional components are realized by executing a program that causes a computer mounted on the peer node to function. The overlay network protocol is a structured overlay Chord using a distributed hash table.

  The routing table 101 is a finger table, and registers the next peer node having an identification value communicable in one hop from the identification value of the peer node.

  The excess delay list 102 registers an identification value range in which the delay time is equal to or longer than the specified time.

  The delay time measuring unit 103 measures the RTT value by periodically transmitting a Keep-Alive message to the next peer node registered in the routing table 101, and calculates the delay time from the RTT value.

  The transmission source request unit 111 transmits a request message for the generated event to the next peer node registered in the routing table 101 toward the destination identification value.

  When the response source message is received, the transmission source list registration unit 112 adds the delay time between the hopped relay peer nodes in order from the transmission source peer node. Then, the identification value range after the next peer node whose delay time is equal to or longer than the specified time is registered in the excess delay list 112.

  The transmission source delay time determination unit 113 determines whether or not the destination identification value of the request message is included in the excess delay list when the request message is further transmitted.

  The relay-side request transfer unit 121 further transfers the received request message to the next peer node.

  When the relay side response transfer unit 122 receives a response message corresponding to the request message, the relay side response transfer unit 122 adds the delay time to the next peer node that transmitted the response message and transfers the response message.

  The transmission source search unit 114 transmits a delayed search request message including the destination identification value to the next peer node registered in the routing table. On the other hand, when it is confirmed that the relay peer node has exceeded the delay, the delay excess notification message is received.

  When the relay side delay excess notification unit 123 receives the delay search request message, if the destination identification value of the search request message is included in the delay excess list of the relay peer node, the relay side delay excess notification unit 123 returns a delay excess notification message. .

  The excess delay list request unit 131 transmits a list request message including the identification value space to the next peer node.

  The excess delay list reply unit 132 returns list information that overlaps the identification value space in the excess delay list held by the next peer node. Further, the excess delay list reply unit 132 preferentially returns list information having a wide identification value range in the excess delay list.

  As described above in detail, according to the call connection method, the peer node, and the program of the present invention, based on the destination identification value in the overlay network, it is immediately determined whether or not the delay time for the peer node is within a specified time. Can be determined.

  By immediately determining whether or not the delay time is within the specified time, it can be applied to various uses. For example, IMS (IP Multimedia Subsystem) / MMD (Multimedia Domain), which is a provider system, and an overlay network constructed with peer nodes can be linked to realize high-quality session control at a low cost. A peer node connected to both the IMS system and the overlay network can reduce the load on the IMS system by preferentially using the overlay network when establishing a session. However, when the number of peer nodes becomes enormous, the number of relay terminals at the time of data search cannot be ignored. In particular, session control that requires real-time performance has a problem that the session establishment time increases. Therefore, according to the present invention, the source peer node estimates the delay time required for the session establishment process on the overlay network. If the delay time exceeds a specified time, a session via the IMS system is established. This makes it possible to guarantee the session establishment time as a system.

  In the various embodiments of the present invention described above, various changes, modifications, and omissions in the scope of the technical idea and the viewpoint of the present invention can be easily made by those skilled in the art. The above description is merely an example, and is not intended to be restrictive. The invention is limited only as defined in the following claims and the equivalents thereto.

1 is a system configuration diagram of an overlay network. It is explanatory drawing of the structured overlay using Chord. It is a sequence diagram in the present invention. It is explanatory drawing showing the step of S31 of FIG. It is explanatory drawing showing the step of S32-S36 of FIG. It is explanatory drawing showing transfer of a delay search request message. It is explanatory drawing showing transfer of a list request message. It is a functional block diagram of the peer node in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Peanode 101 Routing table 102 Delay excess list 103 Delay time measurement part 111 Transmission origin request | requirement part 112 Transmission origin list registration part 113 Transmission origin delay time determination part 114 Transmission origin search part 121 Relay side request transfer part 122 Relay side response transfer part 123 Relay side delay excess notification unit 131 Delay excess list request unit 132 Delay excess list reply unit 2 Source terminal 3 Destination terminal 4 Physical network 5 Overlay network

Claims (14)

A method for determining a delay time in an overlay network virtually configured on a physical network connected by a plurality of peer nodes,
Each peer node has a routing table in which the next peer node having an identification value communicable in one hop is registered, and an excess delay list in which an identification value range in which the delay time is equal to or longer than a specified time is registered,
A first step in which each peer node measures a delay time for each next peer node registered in the routing table;
A second step in which a source peer node transmits a request message including a destination identification value to a next peer node registered in the routing table;
A third step in which the relay peer node further forwards the received request message to the next peer node;
A fourth step in which when the relay peer node receives a response message corresponding to the request message, the relay peer node additionally transmits the delay time with the next peer node that transmitted the response message;
When the source peer node receives the response message, the source peer node adds the delay time between the hopped relay peer nodes in order from the source peer node, and identifies the subsequent peer node and the subsequent peer nodes whose delay time is equal to or longer than the specified time. A fifth step of registering a value range in the excess delay list;
And a sixth step of determining whether or not the destination identification value of the request message is included in the excessive delay list when the source peer node further transmits the request message. Delay time judgment method.   The delay time determination method according to claim 1, wherein the source peer node is a relay peer node that transfers a request message received from the first peer node to the second peer node.   In the first step, a RTT (Round Trip Time) value is measured by periodically transmitting a Keep-Alive message to the next peer node registered in the routing table, and a delay time is calculated from the RTT value. The delay time determination method according to claim 1, wherein: The source peer node transmits a delayed search request message including a destination identification value to a next peer node registered in the routing table;
When the relay peer node receives the delayed search request message, if the destination identification value of the search request message is included in the excess delay list of the relay peer node, returning a delay excess notification message; The delay time determination method according to claim 1, wherein: The peer node sends a list request message including an identification value space to a next peer node;
The said next peer node has a step which returns the list information which overlaps with the said identification value space in the delay excess list which the said next peer node hold | maintains, The any one of Claim 1 to 4 characterized by the above-mentioned. The delay time determination method described.   6. The delay time determination according to claim 5, wherein when the next peer node receives the list request message, the list information having a wide identification value range in the excess delay list is preferentially returned. Method. The excess delay list further includes a registration time for each entry of the identification value range,
When the next peer node receives the list request message including the previous time, the next peer node returns list information of an identification value range in which the registration time after the previous time is recorded in the excess delay list. The delay time determination method according to claim 5. The overlay network protocol is a chord of structured overlay using a distributed hash table (DHT),
The delay time determination method according to claim 1, wherein the routing table is a finger table. A peer node in an overlay network virtually configured on a physical network connected by a plurality of peer nodes,
A routing table in which a next peer node having an identification value communicable in one hop is registered;
Excess delay list with registered identification value range where the delay time is more than the specified time,
A delay time measuring means for measuring a delay time for each next peer node registered in the routing table;
A source request means for transmitting a request message including a destination identification value to a next peer node registered in the routing table;
Relay side request transfer means for further transferring the received request message to the next peer node;
When a response message corresponding to the request message is received, a relay side response transfer means for adding and transferring the delay time with the next peer node that has transmitted the response message;
When the response message is received, the delay time between the hopped relay peer nodes is added in order from the transmission source peer node, and the identification value range after the next peer node in which the delay time is equal to or longer than the specified time is set as the delay time. Source list registration means for registering in the excess list,
A peer node, comprising: a transmission source delay time determination unit that determines whether a destination identification value of the request message is included in the excess delay list when the request message is further transmitted.   The delay time measuring means measures an RTT value by periodically transmitting a Keep-Alive message to the next peer node registered in the routing table, and calculates a delay time from the RTT value. The peer node according to claim 9. A source search means for transmitting a delayed search request message including a destination identification value to a next peer node registered in the routing table;
When the delayed search request message is received, if the destination identification value of the search request message is included in the excess delay list of the relay peer node, a relay side delay excess notification means for returning a delay excess notification message; The peer node according to claim 9 or 10, characterized by comprising: An excess delay list request means for transmitting a list request message including an identification value space to a next peer node;
The delay excess list return means for returning list information that overlaps with the identification value space in the delay excess list held by the next peer node, according to any one of claims 9 to 11. Peer node.   The peer node according to claim 12, wherein the delay excess list reply unit preferentially returns list information having a wide identification value range in the delay excess list. A program for causing a computer mounted on a peer node in an overlay network virtually configured on a physical network connected by a plurality of peer nodes to function,
A routing table in which a next peer node having an identification value communicable in one hop is registered;
Excess delay list with registered identification value range where the delay time is more than the specified time,
A delay time measuring means for measuring a delay time for each next peer node registered in the routing table;
A source request means for transmitting a request message including a destination identification value to a next peer node registered in the routing table;
Relay side request transfer means for further transferring the received request message to the next peer node;
When a response message corresponding to the request message is received, a relay side response transfer means for adding and transferring the delay time with the next peer node that has transmitted the response message;
When the response message is received, the delay time between the hopped relay peer nodes is added in order from the transmission source peer node, and the identification value range after the next peer node in which the delay time is equal to or longer than the specified time is set as the delay time. Source list registration means for registering in the excess list,
When the request message is further transmitted, the computer functions as a transmission source delay time determination unit that determines whether or not the destination identification value of the request message is included in the excess delay list. Program.

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